The central goal of this project is to understand the role of BRD4 as a therapeutic target in acute myeloid leukemia. As a regulator of chromatin, BRD4 is a member of an emerging class of anti-cancer drug targets for which little is understood of its therapeutically-relevant molecular function. This proposal seeks to address this issue by identifying the critical biochemical mechanism employed by BRD4 in leukemia cells that accounts for its desirable properties as a therapeutic target. This will include evaluating which regions of BRD4 are most crucial for its disease-related functions, as well as identifying the key protein constituents of the BRD4 complex that are necessary for leukemia maintenance in experimental mouse models. Efforts will also be made to identify effective therapeutic combinations that can synergize with BRD4 inhibitors to suppress leukemia progression in preclinical leukemia models. This project will rely on integrative approaches, including biochemical, genetic, proteomic, and epigenomic strategies. This research will make extensive use of genetically-engineered mouse models of chemotherapy-resistant leukemia, which will be used to evaluate the in vivo efficacy of various therapeutic manipulations of BRD4 or components of its protein complex. In summary, the long-term goal of this research will be to maximize the clinical benefit of targeting BRD4 in leukemia through an understanding of the detailed mechanism of how this protein works as a regulator of chromatin state.